Magnetic screw driver



M y 1951 F. G. CLARK 2,550,775

MAGNETIC SCREW DRIVER Filed July 13, 1949 Wan 2% 27 78 79 $7 l orwqys.

Patented May 1, 1951 MAGNETIC SCREW DRIVER Frederick G. Clark, Bufialo, N. Y.. assignor of one-half to Wade Stevenson, Buffalo, N. Y.

Application July 13, 1949, Serial No. 104,483 Clai1 ns. (01.145-50) This invention relates to improvements in magnetic'tools of the type in which the workpiece such as a screw, or the like, to be driven is held by magnetic force to facilitate the placing of the workpiece into position to be driven.

One of the obiects of this invention is to provide a magnetic tool of this type, which is so constructed that the driving implement or bit can be readily attached to or removed from the tool. Another object is to provide a tool of this type in which a removable driving implement or bit is held in operative relation to the tool by means of a ma net which also magnetizes the implement so that the work iece becomes attached by magnetic force to the end of the bit. A further obiect is to provide a tool of this type with a shank having at the end thereof a bit holder of non-magnetic material within which a magnet may be arranged, the outer end of the bit holder being formed to receive the driving im lement which is held in place on the tool by the force of the magnet and which driving im lement becomes magnetized to hold the workpiece which is to be driven.

Another obiect is to provide a tool of this type with a magnet which is so arran ed as to serve the two-fold urpose of holding the driving implement on the tool and of ma netizing thedriving im lement to hold a workpiece on the same. It is also an ob ect of this invention to provide .a tool of this type with a removable bit holder A further object of this invention is to provide a tool of this ty e with a bit holder in which a, magnet is embedded and which is provided with a stop shoulder against which a bit abuts when in close proximity to the magnet to prevent transmission of impacts on the bit from being transmitted directly to said magnet. Another object is to provide a bit of improved construction for cooperation with a tool of this type.

Other objects and advantages will be apparent from the following description of one embodiment of the invention and the novel features will be particularly pointed out hereinafter in connection with the appended claims.

' In the accompanying drawings:

Fig. 1 is a fragmentary longitudinal View of a. tool embodying this invention and having a 2 driving implement arranged in position to be inserted into the bit holder of the tool.

Fig. 2 is a similar view thereof, partly in section, showing the driving implement in operative relation to the tool.

Figs. 3 and 4 are respectively transverse sectional views thereof, on lines 3-3 and 4-4, Fig. 2.

Fig. 5 is a longitudinal view, partly in section, similar to Fig. 2, but showing a driving implement or bit of difierent type mounted on the tool.

Fig. 6 is an end view thereof.

Fig. '7 is a fragmentary longitudinal sectional view of the tool shown in Fig. 5 and provided with a bit of modified construction.

Fig. 8 is a longitudinal view, partly in section showing a tool of modified construction.

In the particular embodiment of the invention illustrated in Figs. 1 to '7, 10 represents a shank of a screwdriver or similar tool, only a portion of which is shown in the drawing. This shank may be provided with a handle for rotating the same manually or may be a part of a power driven screwdriver or the like. I I represents a bit holder which is suitably connected with the shank II] in any suitable manner, and which is made of a non-magnetic material, such as non-ferrous metals or certain types of stainless steel. If the shank In is also made of the same non-magnetic material, then the bit holder H and the shank may be formed in one piece. If the shank Ill is made of a magnetic material, then the bit holder ll may be suitably secured thereto in any desired manner.

The bit holder is provided with a bore l2 of any suitable type formed to receive a bar magnet M which may be suitably held within the bore l2 in any suitable manner, either by means of a drive fit of the magnet within the bore, or by soldering, brazing, or the like. The magnet is so arranged within the bit holder that the outer end of the magnet will be spaced within the bit holder at a distance from the outer end thereof. The bore l2 may be circular or noncircular in cross section, and in the particular construction shown, the portion of the bore in which the magnet I4 is arranged is circular, and the bore at the outer end of the bit holder is non-circular to cooperate with a corresponding non-circular'shape of adriving implement or bit, such as the bit l5. In the particular-construction illustrated in Figs. 1 to 4, the shank portion of the bit is of hexagonal cross section, and

consequently, the outer end portion of theborein the bit holder is also hexagonal. In Figs. 5 to '7, the shank portion of the bit is of approximately cross-shaped cross section, and consequently the portion of the bore into which the shank portion of the bit fits is of corresponding cross section. Any other connection may be provided between the driving implement or bit and the bit holder to prevent relative rotation of these two parts. The outer end; lfiiof the driving implement or bit may be of any suitable or desired shape to fit the workpiece which is to be driven by rotation of the shank ill. The driving implement or hit is made of the usual steel employed for! thescrewdriver bits and the like, and is, consequently, magnetic.

As a result of the construction" deseribed-.- and of the use of a bar magnet within. thebitholder. with poles at opposite ends thereof, the magnet holds the bit within the bit holder in theposition shown in Fig. 2, and the magnetism passes through the: bit to the. work-engaging; endit thereof so that a: screw; on similar workpiece WiHZ-b' held-on the endofi thebit. The magnet, consequently; serves the two-fold' purpose of holding the driving implement or bit in the-bit holder and: of. holding the workpiece on'- the: end ofthe bit or driving, implement.

The construction described has the advantage that. the: usual spring; pressed clips, pins, balls, or other holding devices for securing. a bit: or driving implement. in; a. bit. holder may be? dis,- pensed with, since the magnet serves the pur- .pose of holding the bit; in: the bit holder. Furthermore, the; driving implement: can; easily be removed from the bit holder. by' simply pulling on the same sufficiently to overcome the magnetic force, and the'bit or: driving implement can be replacedwith equal: facility by merely insertingthe'shank end ofthe'implement into the bit holder; The construction described has the furtheir advantagev that. the driving implements or bits? can be very easily manufactured to cooperate with: a. toolf of the type described, since the body portion of the bit need not be provided with; an aperturei-or recess-to: cooperate with a detent for holding the: bit: in the; bit holder; This isan important feature, particularly with tools. which are" given severe use in shops or factories; and? in. which the life of a bit is quite short. Consequently; a relatively short bit can besused'so. that the eXpense'-0f replacing of wornout bitsis relatively low;

'I-lrebits or'driving implements; shown in Figs; 1-, and 2 are in the form of Phillips head screw"- drivers, but it will be obvious that the outerends of the. bits maybeofany desired shape to cooperate with screws orbolts of different types. When myimproved-t'oolisto be used in connection: with slotted or recessed head screws, a very short bit or drivingimplement l8, shown in Fig. 7, may be used, in which case, the outer end of then-on-magnetic'bit' holder l'l may serve to engage:the. head of the screw't'o accurately aline the: same while the work engaging endof the screwdriver bit" I8 is seated in the slot or recess of the screw.

Since permanent magnets lose some of their magnetism when subjected to blows, shocks or impacts, 1' have provided means for preventing such shocks or blows on the bits frombeing transmitted to themagnet. For this purpose; the magnet itself and the-borein the bit holder into= which itfits' are made of less diameterthan the" maximum diameter of the non-circular bore intowhichthe bit fits, thus forming a shoulder 4 l7, Fig. 2, at the inner end of that portion of the bore of the bit holder into which the bit fits. The magnet is of such length that it will not extend outwardly beyond the shoulder 11. Consequently, any blows or impacts on the bit will react against the shoulder ll of the bit holder and not against the magnet, thus avoiding loss of magnetism due to such blows. This shoulder also-takes the endwise pressure exerted on the shank it! of the tool against the work, which is desirable, since high power magnets, such as are preferably used on these tools, are somewhat fragile. Preferably the shoulder H extends outwardly to a slight extent beyond the f outer endof' the magnet so that the inner end of the bit" does not contact with the magnet. Theesmallv air gap. thus formed between the end of the magnet and the inner end of the bit does not appreciably reducethe magnetic force exerted on the bit, or on the screw held on the end" of: the bit;

In Figs. 5' to* 7', I have shown a bit in which the: shank I9 is of" approximately cross-shaped crosssection, and in which the bit" holder has the portion. of thebore thereof which receives the bittof corresponding internal cross section. A bit. of this cross' section oflers improved resistance to" the turning of the bit' and the bit holderrrelatively'to each other, as will be readily seen by inspection of Fig. 6; By means of this construction, approximately right-angled longitudihal slots' on grooves 26 are formed in the sides"; of the shank and correspondingly shaped keys or longitudinal projections are formed in the bit" holder to enter the recesses of the shank of' the bit holder. This key and slot construction is capable of transmitting greater torque from the bit holder: to thebit. In the construction shown in Figs; Ste 7, the inner end of the bit liesina plane substantially perpendicular to the longitudinal axis" of the bit, and'this bit has the further advantage that the outer unslotted or peripheral portions 2! of the shank of the bit, which are of substantially cylindrical outer contour; form extend'ed'seats against the annular shoulder 28, Fig; 5', within the bit holder, thus providing a more extended bearing on this shoulder'by the inner end of the bit to further avoidi the transmitting of shocks, blows or pressure' from the bit to the magnet.

In the particular construction shown in Fig. 8', a shank 20 isempl'oyed with which a removable bit holder 21" cooperates and in which the magnet, in addition to the purposes served by it in the construction shown in Figs. 1 to 5, serves the-further purpose of holding the bit holder 2! on the shank 20 of the tool, This is accomplished by making the bit holder 2'! of non-magnetic material and providing a magnet 22 within the bit holder, the magnet being shorter than the bit holder and terminating at both ends in spaced relation to'the' ends of the bit holder. The end portions of the bore of the bit holder are noncircular, one" end being formed to receive the shank 20, which is also non-circular in cross section, and the other end being formed to cooperate with a driving implement or bit 25. The magnet 22 employed in this construction must also be a bar type magnet with the opposite poles thereoflocate'd at its opposite ends. Consequently, one end of this magnet will hold the shank 20 by magnetic attraction, and thus hold the bit holder on the shank of the tool, and the other end of the magnet acts on the driving implement or bit and holds it within the bit holder. The magnet also magnetizes the driving implement so that screws, nuts, or other workpieces may be held by the bit. If the shank 2| is made of the same cross section as the driving implement, it

is, of course, also possibleto reverse the bitholder 2|, since either end of the bit holder will then cooperate with either the shank or driving implement.

The construction shown in Fig. 8 has the advantage that a number of difierent bit holders may be provided to cooperate with the shank 2B. The end of the bit holder which cooperates with the driving implement may be made of various sizes and shapes so as to cooperate with driving implements or bits of difierent sizes and types. In this construction, as well as in the others herein described, the bit holders are preferably made of a non-magnetic material, so that the maximum amount of magnetic force will be available at the end of the driving implement to hold the workpiece. The magnetic force at the outer end of the driving implement is, of course, considerably less than at the end thereof adjacent to or contacting the magnet. Consequently, after the workpiece has been driven into its final position and the tool is removed from the workpiece, the magnetic attraction between the workpiece and the driving implement will not be sufiicient to pull the driving implement out of the bit holder. By making the bit holder of non-magnetic material, so that no liner or non-magnetic sleeve need be provided about the magnet, the outside diameter of the bit holder can be small so that the tool may be used in places where very little room is available for driving a screw.

The construction described has the further advantage that the bit or driving implements used in connection with the magnetic tool may be made of a good grade of tool steel, such as is preferably employed for bits or driving implements of this type.

It will be understood that various changes in the details, materials, and arrangements of parts which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention, as expressed in the appended claims.

I claim as my invention:

1. A magnetic tool comprising a shank by means of which the tool may be rotated, an elongated bit holder of non-magnetic material on said shank, said bit holder having an axial bore, a bar type magnet secured in said bore, the outer end of said magnet terminating in spaced relation to the outer end of said bore, the bore in said bit holder beyond said magnet being noncircular in cross section, and a driving implement of magnetic material having a non-circular portion formed to seat in said non-circular outer end portion of said bore and held in place in said bit holder by said magnet, the portion of the bore in which the magnet is secured being of circular cross section, said portion of non-circular cross section having parts of larger diameter than said portion of circular cross section to form a shoulder against which said. driving implement abuts when held in said bit holder by said magnet.

2. A magnetic tool comprising a shank made of magnetic material and of non-circular cross section and by means of which the tool may be rotated, a bit holder of non-magnetic material having a longitudinal bore therein, a bar magnet secured in said bore of said bit holder with the ends thereof terminating in spaced relation to the ends of said bit holder, one end :of said'bor'ebe ing of cross section corresponding to the cross section of said shank to receive the end portion of said shank and to form adriving connection between said shank and said bit holder, whereby the bit holder is held in operative relation to said shank by means of said magnet, the other end of said bit holder having a non-circular bore for receiving a non-circular member of magnetic material to which rotation may be imparted by rotation of said bit holder and which is held in place in said bit holder by said magnet.

3. A bit holder for use with a shank and bit, said bit holder being of non-magnetic material and having a longitudinal bore, the middle portion of said bore being of smaller diameter than the end portions thereof to form shoulders at the ends of said middle portion of said bore, a bar magnet having poles at opposite ends thereof and secured in said middle portion of said bore, one end of said bore being non-circular in'cross section to slidably receive a shank of corresponding cross section for imparting rotation to said bit holder and the other end of said bore being non-circular in cross section to slidably receive a bit of corresponding cross section for imparting rotation from said bit holder to said bit,

whereby said bit holder is held by magnetic attraction on said shank, and said bit is held on said bit holder by magnetic attraction, said shoulders transmitting end thrust of said shank through said bit holder to said bit without subjecting said magnet to strains.

4. A magnetic tool comprising a shank by means of which the tool may be rotated, an elongated bit holder of non-magnetic material on the end of said shank and having a longitudinal bore which is of non-circular cross section at one end thereof, a bar magnet with the poles at opposite ends thereof arranged entirely within said bore and having the outer end thereof spaced inwardly from said one end of said bit holder and secured to said bit holder, a driving implement of magnetic material having means on the outer end thereof formed to engage a workpiece and a shank of non-circular cross section on the other end thereof formed to slidably and non-rotatably fit into the non-circular end of the bore in said bit holder and adjacent to the magnet, whereby the driving implement will be yieldingly held in said bit holder by the force of said magnet.

5. A magnetic tool comprising a shank by means of which the tool may be rotated, an elongated bit holder of non-magnetic material on the end of said shank and having a longitudinal bore which is of non-circular cross section at one end thereof, a bar magnet with the poles at opposite ends thereof arranged entirely within said bore and having the outer end thereof spaced inwardly from said one end of said bit holder and secured to said bit holder, said end of non-circular cross section constituting a socket terminating at said magnet to receive a shank of similar cross sectional shape of a bit of magnetic material to enable said bit to be rotated by said bit holder, whereby said magnet magnetizes said bit when the shank thereof is in said socket to enable the bit to.support workpieces at the outer end FREDERICK G. CLARK.

(References on following page) file of? this. patent;

UNITED STATES- PATENTS Number Name. Qatg. Bellowsv July 7, 1903 Reynolds Nov. 8, 1932 Walsh Aug. 6, 1935 um n 5 Num r.

Blackburnw-fl-n ay 10; 1938 10 Country Date F anc c- 24, 7: Great Britain of 1885 

